Various devices have been previously used to set fractures of the distal radius in the forearm, but such devices have generally been unsatisfactory. External fixators (hereafter referred to as splints) which have been previously used have generally not been properly designed for selective and continuously adjustable degrees of distraction across the fracture site while allowing for independent adjustment for both appositional and rotational alignment of the same fracture so as to provide the capability of easily returning the distal and proximal fragments to their proper location and to hold them in such locations until the fracture has healed.
Another drawback associated with conventional splints used to treat a fracture is the fact that such splints are comprised of metallic parts, such as rods, screws and pinholding members which span the fracture site. Such metallic parts are opaque to x-rays and do not permit viewing of all aspects of a fracture site in x-ray photographs.
Another drawback with the use of conventional splints for treating a fracture is in the design deficiencies which prevent the selective displacement of the hand and thereby the wrist and distal fragment of the radius in a radial and ulnar direction while isolating this aspect of the fracture reduction from the other three aspects of the fracture reduction, namely, apposition in a dorsal-palmar direction, rotational alignment, and length or degree of distraction. Thus, with conventional splints, it is not possible to manipulate the fracture reduction in a radial and ulnar direction without losing the beneficial adjustments provided by the other three aspects of fracture reduction.
A further drawback associated with conventional splints is that they do not allow for selective extension and flexion of the wrist joint itself. Such extension and flexion can frequently facilitate fracture reduction and/or minimize the risks of extensor tendon "overpull" through wrist extension. Specifically, wrist extension relaxes the tension on the finger extensor tendons and thereby minimizes the risk of producing a stiff hand by allowing more flexion of the metacarpophalangeal joints of the fingers.
U.S. Pat. No. 4,548,199 describes two embodiments of a fracture splint, one of which provides distraction of the distal and proximal bone fragments relative to a fracture site and the other being designed to project an axis from its two major moveable parts that becomes coincident with the rotational axis about which most Colles' type fractures typically rotate. Both of these embodiments have metallic parts which render it difficult to provide x-ray photographs of the fracture site with the splint in place. Moreover, neither embodiment allows for selective adjustment of appositional alignment as appreciated from the anterior-posterior x-ray view, i.e., adjustments of the radioulnar alignment of the fracture. Further, neither embodiment allows for wrist flexion and extension.
U.S. Pat. No. 4,611,586, incorporated herein by reference, describes an improved splint especially for use in treating a Colles' type fracture. Such splint includes an elongated distal element having a traveling block which is movable along the length thereof. One or two distal pins can be carried by the block, the pins being insertable into the metacarpal of the index finger to secure skeletal fixation on the distal side of the fracture site.
A proximal element is pivotally mounted on the proximal end of the distal element and is provided with a pair of pin-receiving holes therethrough. Adjustment means between the distal and proximal elements effects pivotal movement of these two elements relative to each other. Such adjustment means is preferably in the form of a worm and worm gear configured to allow one of the pins to pass through the worm gear and to be inserted into the proximal fragment without interference with the worm gear itself. A worm and rack is preferably used to move the traveling block relative to the distal element.
The distal element of such splint can be made of rigid high strength plastic substantially transparent to x-rays. This permits viewing of the fracture site at all angles in an x-ray photograph, thereby improving the quality of assessment of alignment and enhancing the healing rate. The splint is constructed to allow the distal element of the splint to carry the hand, the wrist and the distal fragment of the fractured radius about an arc with respect to the proximal element of the splint when the proximal element is attached to the radius on the proximal side of the fracture site. The main biomechanical contribution of the splint is the way in which the splint biomechanically complements the pathomechanics of a Colles' type fracture by reducing the fracture displacement about the same axis through which the fragments are displaced at the time of the injury.
In another version of the traveling block on the distal element, the splint has the capability of permitting selective movement of the hand and thereby the wrist and distal fragment of the radius in a radial and ulnar direction by use of a simple adjustment device, such as a wing nut, which can be moved or rotated on the modified traveling block. Moreover, the modified traveling block is designed to allow for selective extension and flexion of the wrist while permitting distracting forces to restore proper length to the radius bone.
The splint also allows selective alignment of the fracture in one plane and/or about one axis of its evolution without substantially altering the alignment in another plane and/or axis. Further, the splint allows for radial and ulnar displacement of the hand on the forearm and thereby displaces the fracture in radial and ulnar directions in a manner which isolates that aspect of the fracture reduction from the other three aspects of fracture reduction.
Although the splint described in U.S. Pat. No. 4,611,586 represented an improvement over previous devices, it does not provide for as many degrees of movement of the hand and wrist as are often required in the setting of a Colles' fracture.
There has not heretofore been provided an external fixator or splint having the advantages exhibited by the splint of the present invention.